<!DOCTYPE HTML>
<!--
     Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/
-->
<html><head>
  <meta charset="utf-8">
  <title>Reference: Masonry layout fragmentation</title>
  <link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
  <style>
html,body {
  color:black; background-color:white; font:10px/1 monospace; padding:0; margin:0;
}
wrapper {
  display: block;
  width: 600px;
  height: 600px;
  overflow: hidden;
}
.columns {
  width: 330px;
  columns: 6;
  column-fill: auto;
  column-gap: 1px;
  background-color: rgba(80,80,80,.2);
  margin-bottom: 10px;
}
.columns:nth-child(2n) {
  background-color: rgba(10,100,10,.5);
}
.grid {
  display: flow-root;
  border: 1px solid;
  gap: 2px;
}
.first { border-bottom-width:0; height:calc(100% - 1px); }
.middle { border-top-width:0; border-bottom-width:0; height:100%; }
.last { border-top-width:0; }
x {
  background: cyan;
  height: 5px;
}
y {
  background: blue;
  height: 10px;
}
.c1 { width: 27px; }
.c2 { width: 37px; }
s { height: 10px; }
z {
  background: pink;
  height: 12px;
}
masonry-track {
  float: left;
  height: 100%;
  gap: 2px;
}
x,y,s,z,masonry-track { display: block; }
masonry-track > * { margin-bottom:2px; }
masonry-track.last > :last-child { margin-bottom:0; }
masonry-track:nth-child(1) { width: 10px; }
masonry-track:nth-child(2) { width: 15px; margin-left:2px; }
masonry-track:nth-child(3) { width: 20px; margin-left:2px; }
</style></head>
<body>
<wrapper>
<div class="columns">
  <div class="grid first">
    <masonry-track><x></x><y class="c1"></y><x></x><y class="c1"></y><x></x></masonry-track>
    <masonry-track><x></x><s></s><x></x><s style="margin-bottom:6px"></s><y class="c2" style="height:5px"></y></masonry-track>
    <masonry-track><x></x><z></z><x></x><z></z></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><x></x><x></x><s style="height:5px"></s><y class="c1"></y><z class="c1"></z><y class="c1" style="height:1px"></y></masonry-track>
    <masonry-track><y class="c2" style="height:5px"></y><z></z></masonry-track>
    <masonry-track><s style="height:5px"></s><x></x><x></x><x></x><x></x><x></x><x></x></masonry-track>
  </div>
  <div class="grid last" style="height:9px">
    <masonry-track><y style="height:9px" class="c1"></y></masonry-track>
    <masonry-track></masonry-track>
    <masonry-track></masonry-track>
  </div>
</div>

<div class="columns">
  <div class="grid first">
    <masonry-track><x></x><y class="c1"></masonry-track>
    <masonry-track><x></x></masonry-track>
    <masonry-track><x></x></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><z></z></masonry-track>
    <masonry-track><x></x><y class="c2"></y></masonry-track>
    <masonry-track><x></x></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><x></x><s style="height:5px"></s><y style="height:4px" class="c1"></y></masonry-track>
    <masonry-track><z></z></masonry-track>
    <masonry-track><x></x><x></x></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><y style="height:6px" class="c1"></y><y class="c1"></y></masonry-track>
    <masonry-track></masonry-track>
    <masonry-track><x></x></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><z></z></masonry-track>
    <masonry-track><x></x><x></x></masonry-track>
    <masonry-track><x></x><x></x></masonry-track>
  </div>
  <div class="grid middle">
    <masonry-track><z class="c1"></z><y style="height:4px" class="c1"></y></masonry-track>
    <masonry-track></masonry-track>
    <masonry-track><x></x><x></x></masonry-track>
  </div>
  <div class="grid last" style="height:6px;">
    <masonry-track><y style="height:6px" class="c1"></y></masonry-track>
    <masonry-track></masonry-track>
    <masonry-track></masonry-track>
  </div>
</div>
<script>
let elts = document.querySelectorAll(".columns");
let heights = [ 48, 18 ];
for (let i = 0; i < heights.length; ++i) {
  elts[i].style.height = heights[i] + "px";
}
</script>
</wrapper>
</body>
</html>
